In the setting of ankle fractures with syndesmosis disruption, fixing the fibula in as much as 30 degrees of external rotation may go undetected using intraoperative fluoroscopy alone.

This study evaluated the feasibility of using a 'self-calibrating' display (EIZO CG277) to perform screenbased threshold perimetry. Such displays incorporate their own integrated photometer, so could potentially be used 'straight out of the box', without the need for time-consuming and costly luminance calibration by skilled experts. Concerns remain, however, due to the fact that the internal calibration of such devices is imperfect (i.e., is limited to a single screen location only) and due to lingering doubts regarding the accuracy of screen-based perimetry in general. To evaluate such a system, automated static threshold perimetry was performed in thirty-two normal-sighted adults. In one condition, participants performed a novel screen-based perimetry test, for which the screen was extensively calibrated using traditional photometric techniques/equipment. In a second condition, the same test was performed, but the display was calibrated using only the screen's integrated photometer (and assuming uniformity across the display). For reference, participants also completed a traditional visual-field assessment using a Humphrey Field Analyzer (HFA). All three tests were performed twice to assess test-retest repeatability (six tests total). The results showed no differences when comparing screen-based perimetric measurements made with internal self-calibration vs full manual calibration (either in terms of mean sensitivity, pointwise sensitivity, test-retest repeatability, or test duration). Furthermore, the accuracy and precision of both were indistinguishable from the current gold standard (HFA), although the HFA was approximately two minutes (~30%) faster. These results indicate that self-calibrating commercial monitors can be used to perform screen-based perimetry almost as well as current clinical devices, and without the need for any specialized knowledge or equipment to setup or maintain. This could facilitate perimetric testing in currently hard-to-reach settings, such as community centers, stroke wards, homes, rural locations, or developing countries.

No abstract

The bone mineral density (BMD) in a given fracture site may affect the outcome of fracture fixation. Low BMD values, such as those occurring in osteoporotic bone, can determine the fixation method and the postoperative care. Evaluation of the BMD is either done subjectively during surgery or by a preoperative measurement. The technique most commonly used to measure BMD preoperatively is dual-energy X-ray absorptiometry (DEXA). DEXA scans have been shown to be site specific [1,2] and therefore may be inaccurate in determining local BMD at the fixation site. Furthermore, in trauma cases, patients frequently do not present with a pre-operative DEXA scan; and the ideal method of assessment would be intraoperative. Intraoperative BMD assessment could be used to guide surgical decisions such as the point of entry of a screw for a fracture plating system or use of locking versus non-locking screw-plate contruct.

The distal radius is a common site of fracture with volar plates and screws as the current clinical practice for fracture fixation [1]. Local measurements of bone quality at the sites of screw insertion aid in providing the most stable fixation with the least amount of hardware, minimizing the risk of construct failure and irritation to soft tissue [2, 3]. The clinical standard for pre-operative bone mineral density (BMD) assessment uses dual x-ray absorptiometry (DEXA). However, DEXA scans provide global BMD values and cannot accurately predict variations in BMD within a given anatomical site [4]. Furthermore, patients frequently present without a pre-operative DEXA scan, so intra-operative assessment would be ideal. We developed a simple sensor system that would be appropriate for assessing local BMD intra-operatively. The system consists of a “smart” Weber clamp instrumented with a single uniaxial strain gage that provides real-time feedback regarding the local BMD.

Rotational ankle injuries are one of the most common musculoskeletal problems treated by orthopaedic surgeons. The distal tibio-fibular syndesmosis may be disrupted during injury resulting in ankle instability. The goal of surgery is to restore anatomic relation of tibia, fibula, and talus. Any malreduction including that of the syndesmosis may result in poor clinical outcomes [1]. While currently accepted radiographic criteria can adequately detect tibio-fibular diasthesis or translation malreductions, it is not yet clear if the currently these criteria are equally suited for detection of rotational malreductions of the tibio-fibular syndesmosis [2]. The goal of this study is to quantify the sensitivity of fluoroscopic measurements of tibio-fibular overlap (TFO) and tibio-fibular clear space (TCS) to rotational malreductions of the syndesmosis. Standard x-ray imaging will be compared with a 3D fluoroscan which will simulate postoperative CT [3].

A commonly accepted treatment method for scaphoid fractures is dorsal percutaneous fixation [1, 2]. This has been shown to decrease the need for cast immobilization and allow faster recovery [3, 4]. For this approach a central screw placement is critical as it provides greater stiffness and load to failure, and allows a longer screw to be inserted which increases screw compression. All of these factors aid in fracture union [5]. However, the complex shape of the scaphoid bone makes central screw placement difficult, as the main axis cannot be easily visualized. Currently, scaphoid screws are placed using K wires guided under 2D fluoroscopy; however, intra-operative 3D fluoroscopy, which can create a CT reconstruction, is becoming more readily available. The goals of this study are to see if there is a significant difference between 2D and 3D fluoroscopic imaging in measuring screw malpositioning (distance off-center) and if there is a difference in repeatability.

No dependable method has yet been established to find time-dependent concentrations of substances injected into the intervertebral disk. This study investigated the feasibility of microdialysis in the measurement of local concentrations of a low-molecular weight drug in the human lumbar disk. A quasi-static experiment and a dynamic computer finite element simulation were used to study the spread of lidocaine in the lumbar disk. Fresh-frozen cadaveric lumbar motion segments were immersed in a 0.1% lidocaine HCl solution for 6 days prior to continuous microdialysis sampling for 30 min at the posterolateral annulus. Samples were collected every 10 min, for a total of three samples per probe. To maintain quasi-static conditions, where the output of lidocaine was equal to the diffusion rate, the microdialysis flow rate was set to 0.6 μl/min. The finite element model treated the disk as poroelastic tissue under compressive load and introduced 1 ml of 4% lidocaine into the nucleus pulposus. Higher microdialysis flow rates suffered from significant losses during consecutive recoveries. Relative recovery in the annulus at 0.6 μl/min was found to be 53.3%±16.2% of the initial solution. This was determined to be a result of low diffusivity of lidocaine through tissue. The FEA model predicted low diffusivity of lidocaine and slow transport to the posterolateral annulus if no fissures were present in the annulus. The results from in vitro experiments and computer simulations showed that while microdialysis can take reliable concentration measurements in the posterolateral annulus, probe placement near a fissure is critical if a measurement is to be made immediately following injection of a drug into the nucleus.